The 3rd Generation Partnership Project, also referred to as “3GPP,” is a collaboration agreement that aims to define globally applicable technical specifications and technical reports for 3rd Generation Systems. 3GPP Long Term Evolution (LTE) is the name given to a project to improve the Universal Mobile Telecommunications System (UMTS) mobile phone or device standard. The 3GPP LTE may define specifications for the next generation of mobile networks, systems, and devices. In one aspect, UMTS has been modified to provide support and specification for the Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN). In 3GPP LTE (i.e., E-UTRA and E-UTRAN) terminology, a base station is called an “Evolved NodeB” (eNB) and a mobile terminal or device is called “user equipment” (UE).
In 3GPP LTE, the eNB regularly transmits a downlink reference symbol (DLRS) that is used by the UEs for channel measurement, such as signal-to-interference ratio (SINR), which may be represented by channel quality information (CQI). Each UE regularly transmits CQI back to the eNB to enable the eNB to perform resource scheduling. Resource scheduling means the eNB allocates modulation schemes, coding rates and subcarrier frequencies to the UEs in order to optimize the downlink and uplink transmissions for each UE.
The data transmitted over a wireless network may be categorized as either non-real-time (NRT) data or real-time (RT) data. Examples of NRT data include data transmitted during web browsing by a UE or text-messaging to a UE, while an example of RT data is voice communication between UEs. Resource scheduling for NRT data is dynamically scheduled by the eNB to each UE at each transmission time interval (TTI). During dynamic scheduling, the UE regularly transmits CQI back to the eNB.
However, in 3GPP LTE the UEs also transmit and receive RT data, specifically voice data which may be carried as Voice over Internet Protocol (VoIP) transmissions. A VoIP session has periodic small data packets at fixed intervals and periodic silence indication (SID) packets at fixed intervals. Unlike NRT data transmission, VoIP transmission is handled using persistent scheduling. In contrast to dynamic scheduling, in persistent scheduling when a UE's downlink reception is enabled, if the UE cannot find its resource allocation (such as modulation and coding schemes (MCS)), a downlink transmission according to a predefined resource allocation is assumed.
VoIP transmission and its associated persistent method of resource allocation present special issues regarding the transmission of CQI by the UEs through an uplink control channel. As such, benefits may be realized by providing systems and methods for reducing the power used to transmit CQI during persistent scheduling.